Anisotropic failure criterion for evaluation of local necking after nonlinear deformation history in sheet metal forming processes

成形性预测是板料成形过程仿真的重要内容之一。工业应用中常用的准则是成形极限曲线（FLC）。flc的一大优点是结合ISO实验测定标准可以很容易地解释模拟或测量数据。然而，传统的FLC仅限于几乎是线性的和不间断的应变路径，即非线性应变增量的变形历史往往与FLC的预测有很大的差异。Volk发表了一种现象学方法，即所谓的广义成形极限概念（GFLC），用于预测具有无限数量非线性应变增量的任意变形历史上的局部颈缩。到目前为止，GFLC还没有考虑材料的各向异性行为。该研究项目的主要重点是根据轧制方向（各向异性）和成形历史对成形极限的实验表征。实验将主要在DFG （INST 95/1268-1）资助的通用试验机BUP1000上进行。在实验数据库的基础上，对应变路径进行参数化，并根据材料的各向异性特性对元模型进行扩展。最后，确定了材料对开发过程的影响，并推导了材料族的标度方法，完成了研究项目。预期的结果使得考虑各向异性材料行为的非线性应变路径的评估成为可能。

The prediction of formability is one of the most important tasks in sheet metal process simulation. The common criterion in industrial applications is the Forming Limit Curve (FLC). The big advantage of FLCs is the easy interpretation of simulation or measurement data in combination with an ISO standard for the experimental determination. However, the conventional FLCs are limited to almost linear and unbroken strain paths, i.e. deformation histories with non-linear strain increments often lead to big differences in comparison to the prediction of the FLC. Volk published a phenomenological approach, the so-called Generalized Forming Limit Concept (GFLC), to predict the localized necking on arbitrary deformation history with unlimited number of non-linear strain increments. Anisotropic material behavior is not considered in the GFLC so far.The main focus of the proposed research project is the experimental characterization of the forming limits depending on the rolling direction (anisotropy) and the forming history. The experiments will be performed mainly on the universal testing machine BUP1000, funded by DFG (INST 95/1268-1). Based on the experimental database a parameterization of the strain paths and an expansion of the metamodel with the anisotropic material behavior takes place. Finally, the identification of the material influence on the developed procedure and derive of a scaling approach for material families complete the research project.The expected results enable the evaluation of non-linear strain path by the consideration of anisotropic material behavior.